packages: add NeedsChromeSource method

Add support for having the Build API indicate that the InstallPackages
call requires Chrome sources to have been synced.

BUG=chromium:1053703, chromium:1086714
TEST=generate

Change-Id: Ic5443a9b15f5ee030b016ff10ad978ee9cfcbd0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/2216237
Reviewed-by: Alex Klein <saklein@chromium.org>
Reviewed-by: George Engelbrecht <engeg@google.com>
Commit-Queue: LaMont Jones <lamontjones@chromium.org>
Tested-by: LaMont Jones <lamontjones@chromium.org>
2 files changed